Exploration of Nanoporous CuBi Binary Alloy for Potassium Storage

The exploration of advanced electrode materials with appropriate structures and compositions is the primary task for nonaqueous potassium ion batteries (PIBs). Herein, 3D nanoporous CuBi anodes are fabricated through a facile chemical dealloying process. The ligaments of this nanoporous alloy are composed of interconnected Bi serving as the active material and Cu decoration as a highly conductive matrix. Such a typical bicontinuous ligament-channel structure is beneficial to overcome the slow K-ion diffusion kinetics as well as electrode expansion on cycling, as evidenced by the high discharge capacity and good rate capability in PIBs. Potassium storage mechanisms in the Bi anodes are investigated through combined techniques to identify the multiple step postassiation process and the charge/discharge products at each stage. Furthermore, it is the first time to report the irreversible phase transition of KBi2 -> Bi upon charge, which seems associated with the ligament pulverization process. These results provide critical insights into the capacity degradation mechanisms of Bi anodes in PIBs. Also, dealloying is proved to be an efficient technology for the rational design of metal/alloy materials for high performance PIBs.